The present invention relates generally to the field of seat belt restraints in motor vehicles. In particular, the present invention relates to a continuously variable energy absorbing mechanism used in seat belt retractors of seat belt apparatuses.
Current seat belt energy absorbing designs have fixed levels of resistance to occupant loading. If the level of resistance is switchable, it is either dependent on the amount of webbing extraction or on outside signals from external sensors that detect the weight of the occupant and/or the crash severity. Unfortunately, the drawback to these designs is that they are costly.
An example of a known energy absorbing mechanism is disclosed in U.S. Pat. No. 6,786,511 (herein incorporated by reference in its entirety), which discloses a belt retractor with a rotor having rotary vanes in a load limiting medium in which each vane has a flow channel. Upon a crash event, the rotor rotates with the belt reel which causes the load limiting medium to flow through the flow channel from one side of the vane to the other. With this fluid flow, energy is consumed and the force acting between the seat belt and the occupant is limited.
U.S. Pat. No. 6,129,385 (herein incorporated by reference in its entirety) discloses a belt retractor that comprises a load limiting apparatus in the form of a spindle with paddles in a circular chamber filled with fluid. When the seat belt webbing is under tension in a crash, the spindle rotates which causes the fluid in the chamber to be pushed into a load limiting assembly via an opening. The fluid flow through the load limiting assembly absorbs some of the force of the crash.
U.S. Pat. No. 6,290,159 (herein incorporated by reference in its entirety) discloses a belt retractor that comprises a load limiter in the form of a hydraulic pump attached to a fluid circuit. During a crash event, the forward displacement of the occupant causes the belt reel and a drive coupled to the belt reel to rotate. The drive rotates the hydraulic pump which, in turn, conveys an incompressible liquid into the closed circuit so that energy is absorbed.